Cardiac resynchronization therapy (CRT) using a bi-ventricular pacemaker is an important treatment option for patients with drug-refractory heart failure and evidence of ventricular dyssynchrony. However, using current selection criteria and implantation techniques, 30-40% of patients undergoing CRT are non-responsive to the treatment. Because CRT is invasive, costly, has significant associated risks, and requires lifelong need of pacing device, there is a clear need for better methods to optimize the treatment. Multiple factors influence patient response to CRT including poor selection criteria and/or non-optimal device implementation. In the implementation of CRT, the position of the left ventricular (LV) pacing lead has a significant role in determining patient response. The overall goals of this project are: 1) to develop an MRI- based methodology to plan and locate the LV pacing lead in the area of latest contraction and 2) test the methodology on a group of patients undergoing CRT. PUBLIC HEALTH RELEVANCE: We propose to develop methodology to use magnetic resonance imaging (MRI) to plan left ventricular lead placement in patients undergoing cardiac resynchronization therapy (CRT) using a bi-ventricular pacemaker. The project involves development and validation of software for the display of regional ventricular dyssynchrony and myocardial scar burden by MRI. The MRI based methodology will then be evaluated in a series of patients to test its ability to improve outcomes by improving lead placement.